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nvme-multipath: Add visibility for round-robin io-policy

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This patch helps add nvme native multipath visibility for round-robin
io-policy. It creates a "multipath" sysfs directory under head gendisk
device node directory and then from "multipath" directory it adds a link
to each namespace path device the head node refers.

For instance, if we have a shared namespace accessible from two different
controllers/paths then we create a soft link to each path device from head
disk node as shown below:

$ ls -l /sys/block/nvme1n1/multipath/
nvme1c1n1 -> ../../../../../pci052e:78/052e:78:00.0/nvme/nvme1/nvme1c1n1
nvme1c3n1 -> ../../../../../pci058e:78/058e:78:00.0/nvme/nvme3/nvme1c3n1

In the above example, nvme1n1 is head gendisk node created for a shared
namespace and the namespace is accessible from nvme1c1n1 and nvme1c3n1
paths.

For round-robin I/O policy, we could easily infer from the above output
that I/O workload targeted to nvme1n1 would toggle across paths nvme1c1n1
and nvme1c3n1.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
This commit is contained in:
Nilay Shroff
2025-01-12 18:11:44 +05:30
committed by Keith Busch
parent 316dabe608
commit 4dbd2b2ebe
4 changed files with 130 additions and 4 deletions
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18
drivers/nvme/host/nvme.h
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@@ -534,10 +534,11 @@ struct nvme_ns {
struct nvme_ns_head *head;
unsigned long flags;
#define NVME_NS_REMOVING 0
#define NVME_NS_ANA_PENDING 2
#define NVME_NS_FORCE_RO 3
#define NVME_NS_READY 4
#define NVME_NS_REMOVING 0
#define NVME_NS_ANA_PENDING 2
#define NVME_NS_FORCE_RO 3
#define NVME_NS_READY 4
#define NVME_NS_SYSFS_ATTR_LINK 5
struct cdev cdev;
struct device cdev_device;
@@ -933,6 +934,7 @@ int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo);
int nvme_dev_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags);
extern const struct attribute_group *nvme_ns_attr_groups[];
extern const struct attribute_group nvme_ns_mpath_attr_group;
extern const struct pr_ops nvme_pr_ops;
extern const struct block_device_operations nvme_ns_head_ops;
extern const struct attribute_group nvme_dev_attrs_group;
@@ -955,6 +957,8 @@ void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys);
void nvme_failover_req(struct request *req);
void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl);
int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl,struct nvme_ns_head *head);
void nvme_mpath_add_sysfs_link(struct nvme_ns_head *ns);
void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns);
void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid);
void nvme_mpath_remove_disk(struct nvme_ns_head *head);
int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id);
@@ -1009,6 +1013,12 @@ static inline void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)
static inline void nvme_mpath_remove_disk(struct nvme_ns_head *head)
{
}
static inline void nvme_mpath_add_sysfs_link(struct nvme_ns *ns)
{
}
static inline void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns)
{
}
static inline bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
{
return false;